Staphylococcus aureus is one of Staphylococcus microorganisms which are resident bacteria on human or animal skins or digestive tracts (intestines) (enteric bacteria), and known as one of the bacteria causing purulent diseases or food poisoning in humans or animals. It is also known that, even when an animal infected with food poisoning-causing bacteria is free itself from any symptoms, there is a possibility that a human in contact with this animal is infected with the food poisoning-causing bacteria or that the food poisoning-causing bacteria is deposited on a product made from this animal, resulting in a significant reduction in the value of the animal itself or the value of the product made from this animal. Amongst, Staphylococcus aureus is believed to be related strongly with mastitis in cows.
The annual economical loss due to cow mastitis is reported to be 60 billion yens in Japan. Staphylococcus aureus is one of major pathogens which cause cow infectious mastitis, and considered to be treated less effectively with antibiotics unlike to environmental mastitis bacteria such as Escherichia coli and environmental Streptococcus. 
There are at least 30 known pathogenic factors as cell components of Staphylococcus aureus, and Protein A, fibronectin-binding protein, clumping factor, and lipoteichoic acid are known as molecules localized in cells. In addition, coagulase and staphylokinase are known as enzymes relating to the pathogenicity.
Those known as toxins released out of cells are those in the enterotoxin group related strongly with food poisoning in humans, TSST-1 related to sepsis and leucocidin exerting a cytotoxic activity to leucocytes as immunocompetent cells.
While investigations focusing mainly on cell components have been made so far as approaches to vaccines for Staphylococcus aureus-related mastitis, it is still unsuccessful in discovering a main component which has an evident infection-preventing effect. This is because partly of difficulty in obtaining a preventive effect attributable to a single molecule due to the isolate-based variation in the situation of holding pathogenic factors as cell components. To overcome this, an attempt was made to use a vaccine employing all cells as antigens, but it was unsuccessful in imparting an evident infection-preventing effect similarly to the cases described above. This may partly be caused by such a background that the immune imparted to a milk is insufficient or the evaluation itself is not conducted in most of the cases. While use of a supernatant component as a vaccine antigen is also investigated, a study considering the actual condition of the mastitis-derived microorganisms as active ingredients contained in the supernatant has not been made yet, resulting in a difficulty in imparting infection-preventing effect. It is also believed that it is difficult, only with the supernatant component, to obtain an infection-preventing effect which is sufficient also immunologically. The background is considered to be responsible for unsuccessful development so far of vaccines effective to Staphylococcus aureus-related cow mastitis.
There are known technologies for preventing infection with Staphylococcus aureus including a mastitis vaccine using Staphylococcus aureus as an immunogen which is contained in a vaccine vehicle constituted from a liposome containing methylglutarylated poly(glycidol) (Patent Document 1) or a method for treating or preventing Staphylococcus aureus (S. aureus) infection in avian or mammalian animals by administering a therapeutically effective amount of a pharmaceutical composition including one or more digestive enzymes to the avian or mammalian animals (Patent Document 2). However, vaccines capable of being used for mastitis, including other pathogens, in actual sites of use such as farms do not exist currently in Japan.